Rack-and-pinion steering gear, in particular for motor vehicles

ABSTRACT

A rack-and-pinion steering gear which includes a steering shaft provided with a driving pinion that engages a rack which is arranged laterally with respect to the steering shaft and which rack is capable of axial movement. A stop formed by a snap ring anchored in a borehole of the steering housing in combination with a supporting part retained by the snap ring supports a thrust piece which is pressed by a spring element against the back of the rack, is guided in the housing borehole and serves to guide the rack in a bedding of the thrust piece. The rack-and-pinion steering gear is further characterized by the supporting part for the spring element or the thrust piece being formed by at least one inwardly directed bar which is firmly connected to the snap ring and which lies in the same plane as the snap ring. In this manner, an elastically yielding thrust piece support which requires less parts and is simple to install is provided in order to render the rack-and-pinion steering gear of the invention suitable for large scale production for use in smaller passenger cars.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a rack-and-pinion steering gear, in particularfor motor vehicles.

In such steering gears, the steering shaft bears a driving pinion thatengages a rack which is arranged laterally with respect to the steeringshaft and which is movable axially. To support the rack and to pressinto the driving pinion, there is provided a thrust piece that isretained in a housing borehole and that rests against the back of therack by virtue of spring force. The thrust piece is supported via a stopin the housing. As stop, there is provided a snap ring, anchored in ahousing borehole, and a supporting part, retained against said ring.

2. Description of the Prior Art

In a steering gear known from EP A 0 124 418, a disc lies as supportingpart on the snap ring and, supported against the disc, there is a springthat keeps the thrust piece resting against the rack without clattering.This kind of thrust piece support has a very simple structure but, toadjust the play, one must measure both the thickness of the snap ringand the thickness of the disc. In addition, there is the fact that thedisc must be mounted and must be held during the assembly of the snapring.

The object of the invention is to find a reasonably priced andelastically yielding thrust piece support that will require less partsand that will use parts that are simple to install. Such a design shouldbe suitable particularly for the large-series production ofrack-and-pinion steering gears to be used in smaller passenger cars.

SUMMARY OF THE INVENTION

The support of the thrust piece according to the invention has, as asupporting part, at least one bar that is firmly connected with the snapring and that is aimed toward the center of the thrust piece. This barreplaces the disc that is now present in the state of the art. If onemakes the bar sufficiently stiff, then a spring element--for pressingthe thrust piece on--can be supported on the bar. In this case, onetherefore needs only two parts for the thrust piece support: the snapring and one spring. One can also make the bar--which is connected tothe snap ring--elastically. The bar then directly supports the thrustpiece and at the same time acts as a spring element. One thus needs onlya single part for the thrust piece support. The snap ring is anchored ina groove of the thrust piece housing borehole. The play of the thrustpiece can be adjusted easily by means of the selective assembly of snaprings having different thicknesses.

In one particular embodiment, a circular plate is molded as bar in thecenter of the snap ring; said bar is connected to the snap ring by aconstriction. The bar lies in the same plane as the snap ring a servesas supporting plate either for the spring element or for the thrustpiece. The bearing is simpler and the production costs are lower becauseone only needs one part when the thrust piece is supported directly.

The supporting part can also be made with bars that extend in starfashion toward the snap ring and that rest on projections of the snapring. One of the bars is attached to one projection. This design issuitable for supporting the thrust piece by means of a spring element.

According to another embodiment, one can provide on the snap ringequally spaced and inward-protruding bars on which the spring elementrests. The snap rings with the inside-located spring supports can bemade cheaply by means of precision stamping and subsequent hardening.

Finally, the invention also comprises another embodiment with a springelement integrated into the snap ring. For this purpose, there isprovided a bar that is molded upon the snap ring and that extends intothe center of the snap ring. Depending on the required spring stiffness,the bar can be made with lesser thickness than the snap ring or with thesame thickness as the snap ring. The bar rests on a nose of the thrustpiece and presses said piece into the rack. One can therefore eliminatea separate spring element.

The invention is described below in greater detail with the help of fourexemplary embodiments illustrated in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is partial longitudinal profile through a rack-and-pinionsteering gear.

FIG. 2 is a view in the direction of arrow II in FIG. 1 with the housinglid omitted.

FIG. 3 is an enlarged view of a variant of the snap ring including thesupporting plate.

FIG. 4 is a partial view in the direction of arrow IV in FIG. 3.

FIG. 5 is an enlarged view of another variant of the invention.

FIG. 6 is a profile along FIG. 1 of another variant and

FIG. 7 is a view in the direction of arrow VII in FIG. 6 with thehousing lid omitted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A driving pinion 2--positioned in a steering housing 1 and capable ofbeing rotated by a steering wheel--engages a rack 3. Rack 3 and housing1 surrounding it is not illustrated with its entire length on both sidesof the driving pinion for reasons of simplicity. On the side oppositedriving pinion 2, a thrust piece 6--loaded by a spring element 5--isguided in a housing borehole 4. Thrust piece 6 has a bedding 7 that isadapted to rack 3 and that is lined with a plastic insert 8. Accordingto the invention, thrust piece 6 rests against a snap ring 11 that isinserted in a groove 10 of housing borehole 4. As one can see from FIG.2, snap ring 11 has a molded--on support plate 12 against which springelement 5 is supported. To compensate for the play, one can insert snaprings 11 of different thickness (gradation 0.05 mm) in groove 10. Inother words, during assembly, one selects a snap ring 11 that iscoordinated for the particular production tolerance. For betterabsorption of its axial movements, one can insert a sealing ring inthrust piece 6. Housing borehole 4 is closed off by a lid 14.

FIGS. 3 and 4 show a modified snap ring 15 that has projections 16.Projections 16 serve as supporting surfaces for bars 17 of a star-shapedsupporting plate 18 that also serves to support a spring element 6 (FIG.1).

Supporting plate 18 is best attached to one of bars 17 on snap ring 15by a rivet 20 or the like.

A snap ring 21 according to FIG. 5 has equally spaced, inward-pointedbars 22 to support the spring element.

In FIGS. 6 and 7, a spring element is integrated into a snap ring 23.Snap ring 23 has a molded-on bar 24 as spring element; said bar extendsinto the center of the ring. To achieve adequate elasticity, bar 24 canhave a smaller thickness than snap ring 23. Bar 24 acts as a bendingspring. Thrust piece 25 has a nose 26 that is located in the middle andbar 24 rests on said nose in a prestressed manner.

We claim:
 1. A rack-and-pinion steering gear suitable for use in motorvehicles which comprises:a steering housing having a borehole therein; asteering shaft provided with a driving pinion that engages a rack havinga back and which is arranged laterally with respect to the steeringshaft and which rack is capable of axial movement; a stop formed by asnap ring anchored in the housing borehole in combination with asupporting part retained by the snap ring; said rack is guided in abedding of a thrust piece located in the steering housing; the thrustpiece is pressed by a spring element against the back of the rack, isguided in the housing borehole in the steering housing and rests on thestop; wherein the supporting part for the spring element or the thrustpiece is formed by at least one inwardly directed bar which is firmlyconnected to the snap ring and which bar lies in the same plane as thesnap ring.
 2. A rack-and-pinion steering gear as claimed in claim 1wherein the bar comprises a substantially circular plate that isintegral with the snap ring and the bar is connected to the snap ring bya constriction.
 3. A rack-and-pinion steering gear as claimed in claim 1wherein the housing borehole is provided with a groove and snap rings ofdifferent thickness can be inserted in the groove to compensate for playin the groove.
 4. A rack-and-pinion steering gear as claimed in claim 1wherein the snap ring is provided with a plurality of projections;thesupporting part is provided with bars that extend in a star-shapetowards the snap ring and rest on the projections of the snap ring; andwherein one of the bars is attached to a projection.
 5. Arack-and-pinion steering gear as claimed in claim 4 wherein the bar isattached to the projection by a rivet.
 6. A rack-and-pinion steeringgear as claimed in claim 1 wherein the supporting part of the snap ringincludes several evenly spaced bars which protrude inwardly.
 7. Arack-and-pinion steering gear as claimed in claim 1 wherein the bar ismolded on the snap ring and extends into the center of the snap ring,and the bar rests elastically against a nose that is formed in themiddle of the thrust piece.